Research On Optimization Of Container COW Mechanism Based On Dynamic Prefetching Strategy

With the development of virtualization technology,uses are paying more and more attention to the applications and services themselves,and hope that the bloated underlying operating system and other environments can be reused.Therefore,the generation of container technology satisfies the user's demand for lightweight virtualization.At present,Docker is the mainstream container solution,and its storage drivers adopt CoW(Copy-onWrite)technology.The underlying image files exist as a read-only layer,and the container layer launched by the image files acts as a read-write layer for storing private data of the container individual.The CoW mechanism satisfies the container's need to share the same image files.However,since for a single container,each time you access the image file,you need to copy it up to the upper read/write layer,which will bring additional overhead,especially when the accessed image file is large.The extra overhead becomes unnegligible.Therefore,it is necessary to optimize the overhead caused by the container CoW mechanism.In order to solve the problem of the overhead caused by the CoW mechanism to the applications/services in the container,the DPSO system,a Docker container CoW mechanism optimization system based on dynamic prefetching strategy is designed and implemented.The optimization direction of DPSO is based on the correlation between Docker images and containers,forming the history records corresponding to each image,and filtering the history records through dynamic prefetching strategy.Finally,according to the screening results,some image files are copied up at the beginning of the container startup.Through this strategy,DPSO can pre-copy up the files that are most likely to perform copy up to the read/write layer of the container in the initial stage of container startup,thus eliminating the overhead caused by the CoW mechanism during the application runtime.The experimental results show that the accuracy of dynamic prefetching strategy is more than 78% in complex scenario of the DPSO system.Based on the accuracy of prefetching,the overhead caused by CoW mechanism can be effectively eliminated.